Phylogenetic analyses of the putative M (ORF 6) and N (ORF 7) genes of porcine reproductive and respiratory syndrome virus (PRRSV): implication for the existence of two genotypes of PRRSV in the U.S.A. and Europe

Abstract

The putative membrane (M) protein (ORF 6) and nucleocapsid (N) protein (ORF 7) genes of five U.S. isolates of porcine reproductive and respiratory syndrome virus (PRRSV) with differing virulence were cloned and sequenced. To determine the genetic variation and the phylogenetic relationship of PRRSV, the deduced amino acid sequences of the putative M and N proteins from these isolates were aligned, to the extent known, with other PRRSV isolates, and also other members of the proposed arterivirus group including lactate dehydrogenase-elevating virus (LDV) and equine arteritis virus (EAV). There was 96-100% amino acid sequence identity in the putative M and N genes among U.S. and Canadian PRRSV isolates with differing virulence. However, their amino acid sequences varied extensively from those of European PRRSV isolates, and displayed only 57-59% and 78-81% identity, respectively. The phylogenetic trees constructed on the basis of the putative M and N genes of the proposed arterivirus group were similar and indicated that both U.S. and European PRRSV isolates were related to LDV and were distantly related to EAV. The U.S. and European PRRSV isolates fell into two distinct groups, suggesting that U.S. and European PRRSV isolates represent two distinct genotypes.

Sequence comparison of open reading frames 2 to 5 of low and high virulence United States isolates of porcine reproductive and respiratory syndrome virus

“…Again, the least virulent isolate, ISU3927, displayed higher variation in ORFs 2 to 4 (Fig. 2) and little variation in ORFs 5 to 7 compared with other US isolates (Meng et al, 1995). The amino acid sequence identity between the isolate ISU3927 and other US isolates is 91-93% in ORF 2, 86-88% in ORF 3, 92-93 % in ORF 4 and 89-92 % in ORF 5.…”

“…The nucleotide sequence identity between LV and US isolates was 65-67% in ORF 2, 61-64% in ORF 3, 63-66% in ORF 4 and 61-63 % in ORF 5. Extensive genetic variation in ORFs 6 and 7 between LV and US PRRSV has also been reported previously (Meng et al, 1995).…”

“…The predicted products of ORFs 2 to 4 have the characteristics of membrane-associated proteins (Conzelmann et al, 1993;Meulenberg et al, 1993 ;Morozov et al, 1995); however, their translation products were not detected in virusinfected cell lysates or virions (Meulenberg et al, 1995), Antigenic, genetic and pathogenic variations have been reported among different PRRSV isolates. The US and European PRRSVs represent two distinct genotypes (Meng et al, 1995). Antigenic variability exists not only between US and European isolates but also among US isolates (Wensvoort et al, 1992;Nelson et al, 1993).…”

Indian porcine reproductive and respiratory syndrome virus bears discontinuous deletion of 30 amino acids in nonstructural protein 2

“…The causative agent, PRRSV, is an enveloped, single-stranded, positive-sense RNA virus with an approximate diameter of 50-65 nm and belongs to the family Arteriviridae in the order of Nidovirales [8,31]. There are two distinct genotypes of PRRSV: genotype 1 (European) and genotype 2 (North American) which, share only about 60 % identity on the nucleotide level, while individual PRRSV isolates within genotypes varies approximately 20 % in nucleotide sequence [13,19]. The genome size of PRRSV is about 15 kb possessing a 5 0 -capped structure, a 3 0 -polyadenylated tail, and at least nine open reading frames (ORF1a, ORF1b and ORFs 2 to 7) flanked by 5 0 -and 3 0 -untranslated regions (UTR) [9,20].…”

Different immunological features of two genetically distinct type 2 porcine reproductive and respiratory syndrome (PRRS) viruses

“…PRRSV is a member of the family Arteriviridae in the order Nidovirales (Cavanagh, 1997) and an enveloped virion containing a single-stranded positive-sense RNA genome. PRRSV has been classified into two genetically and antigenically distinct groups, European (Type 1) and North American (Type 2) genotype (Meng et al, 1995;Murtaugh et al, 1995). Remarkable genetic and antigenic variations have been observed between the genotypes and within the same genotype (Yang et al, 1999;Cheon and Chae, 2000;Key et al, 2001;Forsberg et al, 2002;Pesch et al, 2005;Fang et al, 2007;Zhou et al, 2009).…”